The present invention relates to medical devices and methods of using such devices. More particularly, the invention relates to instruments and methods to measure the length of the cervix in the fornix vaginae and the dilation of the cervix uteri.
Preterm labor, or labor before 37 weeks gestation, has been reported in 7 to 10 percent of all births but accounts for more than 85 percent of all perinatal complications and death. Rush et al., BMJ 2:965-8 (1976) and Villar et al., Res. Clin. Forums 16:9-33 (1 994), which are both incorporated herein by reference. An inverse relationship between cervical length in the fornix vaginae and the risk of preterm labor has also been observed. Anderson et al., Am. J. Obstet. Gynecol. 163:859 (1990); lams et al., N. Eng. J. Med. 334:567-72 (1996) and Heath et al., and Ultrasound Obstet. Gynecol. 12:312-7 (1998), which all are incorporated herein by reference. Accordingly, many physicians find it useful to examine the cervix in the fornix vaginae as part of normal prenatal care in order to assess risk of preterm labor.
It has long been known that the cervix normally undergoes a series of physical and biochemical changes during the course of pregnancy, which enhance the ease and safety of the birthing process for the mother and baby. For example, in the early stages of labor the tissues of the cervical canal soften and become more pliable, the cervix shortens (effaces), and the circumference of the proximal end of the cervical canal begins to increase at the internal os. As labor progresses, growth of the cervical diameter propagates to the distal end of the cervical canal, toward the external os. In the final stages of labor, the external os dilates allowing for the unobstructed passage of the fetus.
In addition to the physical and biochemical changes associated with normal labor, genetic or environmental factors, such as medical illness or infection, stress, malnutrition, chronic deprivation and certain chemicals or drugs can cause changes in the cervix. For example, it is well known that the in utero exposure of some women to diethylstilbestrol (DES) results in cervical abnormalities and in some cases gross anatomical changes, which leads to an incompetent cervix where the cervix matures, softens and painlessly dilates without apparent uterine contractions. An incompetent cervix can also occur where there is a history of cervical injury, as in a previous traumatic delivery, or as a result of induced abortion of the cervix is forcibly dilated to large diameters, Details of the incompetent cervix are discussed in Sonek, et al., Preterm Birth, Causes, Prevention and Management, Second Edition, McGraw-Hill, Inc., (1993), Chapter 5, which is incorporated by reference herein.
Cervical incompetence is a well recognized clinical problem. Several investigators have reported evidence of increased cervical os diameter as being consistent with cervical incompetence (see Brook et al., J. Obstet. Gynecol. 88:640 (1981); Michaels et al., Am. J. Obstet. Gynecol. 154:537 (1986); Sarti et al., Radiology 130:417 (1979); and Vaalamo et al., Acta Obstet. Gynecol. Scan 62:19 (1983), all of which are incorporated by reference herein). Internal os diameters ranging between 15 mm to 23 mm have been observed in connection with an incompetent cervix. Accordingly, a critical assessment in the diagnosis of an incompetent cervix involves measurement of the internal cervical os diameter.
There are also devices and methods to measure the diameter of the external cervical os. For example, cervical diameter can be manually estimated by a practitioner""s use of his or her digits. Although an individual practitioner can achieve acceptable repeatability using this method, there is significant variation between practitioners due to the subjective nature of the procedure. To address these concerns, various monitoring and measuring devices and methods have been developed. For example, an instrument for measuring dilation of the cervix uteri is described in U.S. Pat. No. 5,658,295. However, this device is somewhat large, leading to a risk of injury to the fundus of the vagina or cervical os. Additionally, it is not disposable and requires repeated sterilization. Another device for measuring cervical diameter is described, for example, in U.S. Pat. No. 6,039,701. In one version, the device described therein has a loop element which is secured to the cervix. The loop expands or contracts with the cervix and a gauge is coupled to the loop for measuring changes in the loop dimension. Such changes can then be detected by electronic means. Accordingly, this device is rather complex and expensive to manufacture.
Even if a woman is found to have an apparently normal internal cervical os diameter, there may nonetheless be a risk for preterm labor and delivery. Currently, risk assessment for preterm delivery remains difficult, particularly among women with no history of preterm birth. However, the findings that preterm delivery is more common among women with premature cervical shortening or effacement suggest that measuring the length of the cervix would be predictive for preterm labor.
Currently, a physician has at least two options to measure the length of the cervix in the fornix vaginae. One such method involves serial digital examination of the cervix by estimating the length from the external cervical os to the cervical-uterine junction, as palpated through the vaginal fornix. Although this is useful for general qualitative analysis, it does not afford an easy nor accurate measurement of the length of the cervix from the external cervical os to the cervical-uterine junction (also described herein as the length of the cervix extending into the vagina) and, therefore, does not provide an accurate assessment of the risk of preterm labor. Despite the use of gloves, vaginal exams always carry with them the risk of transmitting infectious agents, especially to the fetal membranes, the lining and/or muscle of the uterus, or the fetus itself.
Another method involves real-time sonographic evaluation of the cervix. This method provides relatively quick and accurate cervical dimensions. However, it requires expensive equipment, highly skilled operators, as well as skill in interpretation of results, which are all subject to human error. Also, due to the expense of the procedure many women, especially those without proper health insurance, cannot afford to have a sonographic test performed.
It would be beneficial if there were an instrument a practitioner could use to measure the cervix quickly and accurately, and with little material expense. Although there are several instruments available for determining various dimensions of the uterus, there is no suitable instrument for measuring the length of the cervix in the fornix vaginae. For example, U.S. Pat. No. 4,016,867 describes a uterine caliper and depth gauge for taking a variety of uterine measurements, which although useful for fitting an intrauterine contraceptive device, is not capable of measuring the length of the cervix in the fornix vaginae due to interference by the caliper""s wings. In fact, similar devices described in U.S. Pat. Nos.: 4,224,951; 4,489,732; 4,685,747; and 5,658,295 suffer from similar problems due to their use of expandable wings or divergable probe tips. These devices are also relatively sophisticated, making them expensive to manufacture and purchase. U.S Pat. No. 3,630,190 describes a flexible intrauterine probe, which is particularly adapted to measuring the distance between the cervical os and the fundus of the uterus. The stem portion of the device has a plurality of annular ridges spaced apart from each other by a predetermined distance, preferably not more than one-half inch apart. However, this device is not adapted for accurately measuring the length of the cervix in the fornix vaginae because of the lack of an appropriate measuring scale and a stop for automatically recording the measurement.
Accordingly, there is currently no commercially available, quick, inexpensive as well as accurate device to assess the risk of preterm labor by measuring the length of the cervix in the fornix vaginae. Therefore, many women at risk for preterm labor may be unaware of the risk to their pregnancy and their unborn child. If such a device were available, many more women would be better informed about the course of their pregnancy and would then be able to make better choices about becoming pregnant at all, or about managing their pregnancy to reduce the risk of preterm labor and injury to the unborn child.
Thus, there exists a need for a simple and inexpensive device that can be used to determine the length of the cervix in the fornix vaginae and, thus, predict the risk of preterm labor, as well as other conditions. There is also a need for such a device that can measure the dilation of the cervix uteri, to provide an overall assessment of the cervix and to determine the particular stage of labor. Ideally, the device should be adapted for use by a physician or obstetrician or even a trained nurse in the doctor""s office or clinic. Preferably, the device should be disposable or capable of being sterilized. In addition, it is desirable that device record the measurement automatically. The present invention satisfies these needs and provides related advantages as well.
The present invention provides devices and methods for determining a dimension of a female reproductive organ.
The present invention provides for a device for determining a dimension of a female reproductive organ, such as, e.g., the cervix, and includes a hollow member with a distal end, a proximal end, and a lumen, a measurement member, insertable into the lumen of the hollow member, having a distal portion, a proximal portion, and a measurement scale along the proximal portion, a flange attached to the distal end of the hollow member, and a light element that is oriented to emit light toward the distal end of the measurement member. The measurement scale of the measurement member, in one embodiment, includes a plurality of color-coded incremental markings. In one embodiment of this device, the light element is located within the distal portion of the measurement member. Here, the device also includes a handle attached to the proximal portion of the measurement member and having an interior space, a power source located within the interior space of the handle, and lead wires attached to the power source and extending through the measurement member to electrically couple the light element with the power source. Alternatively, the light element is a light emitting component that is attached to the hollow member using appropriate attachment means, such as, e.g., snap-on clips and the like. With this alternative embodiment, the device may further include an external power source and lead wires to electrically couple the light emitting component of the light element to the power source. This device, in one embodiment, also includes a locking mechanism to fix the position of the measurement member within the hollow member. Here, the hollow member includes an opening on its proximal portion, and a locking mechanism having a collar with an opening for the insertion of a fastening member is placed around the circumference of the hollow member. Also, a fastening member, such as, e.g., a screw, is provided that is inserted into the opening of the collar, into the opening of the hollow member, and into contact with the measurement member in order to engage and secure the position of the measurement member. In another embodiment of this device, the flange includes a body that is offset from the hollow member, a plurality of measurement markings on the body, and an opening through which the measurement member may be advanced. The flange is preferably manufactured from a substantially translucent material. The device may also include an elongated slot that extends lengthwise along a portion of the hollow and a pin on the measurement member that further comprises a protrusion disposed on an internal surface of the hollow member and the measurement member further comprises a flat surface extending lengthwise along the measurement member. Here, the protrusion and the flat surface are capable of being engaged to fix and maintain the position of the measurement member within the hollow member. In another embodiment, the hollow member further comprises an opening on a circumference of the hollow member for the insertion of a fastening member, such as, e.g., a screw, there through, the measurement member further comprises a flat surface extending lengthwise along the measurement member, and a fastening member is provided that is insertable into the opening of the hollow member to engage the flat surface of the measurement member and fix the position of the measurement member within the hollow member. Alternatively, the hollow member further comprises a slot having a first wall and a second wall, the slot extending lengthwise along substantially the entire length of the hollow member, and the measurement member further comprises a protrusion extending into the slot. With this embodiment, the protrusion of the measurement member is capable of being engaged with a wall of the slot to fix the position of the measurement member within the hollow member.
The present invention further provides for a device for determining a dimension of a female reproductive organ that includes a hollow member having a distal end, a proximal end, and a lumen, a measurement member insertable into the lumen of the hollow member and having a distal portion, a proximal portion, and a measurement scale disposed along the proximal portion, a substantially translucent flange attached to the distal end of the hollow member and having a body offset from the hollow member, an opening extends through the slot. The slot and pin prevent excessive rotation of the measurement member within the hollow member, thereby increasing the ease of operation of the device.
The present invention also provides for a device for determining a dimension of a female reproductive organ that includes a hollow member having a distal end, a proximal end, and a lumen, a measurement member having a distal portion, a proximal portion, and a measurement scale along the proximal portion, wherein the measurement member is insertable into the lumen of the hollow member, a flange with a body offset from the hollow member and an opening for advancement of the measurement member there through, wherein the flange is attached to the distal end of the hollow member, and a light element disposed within the measurement member. In one embodiment of this device, the light element is located within the distal portion of the measurement member and at least the distal portion of the measurement member is substantially translucent. Alternatively, the entire measurement member is substantially translucent. In another embodiment, the hollow member includes a plurality of ports at the distal end of the hollow member in order to allow light emitted from the light element to pass through the hollow member. In another embodiment, both the hollow member and the measurement member are both substantially translucent. This device may also include a handle attached to the proximal portion of the measurement member, a power supply housed within the handle, and a plurality of leads electrically coupling the power supply with the light element, wherein the leads extend from the power supply through the measurement member and to the light element. In addition, several embodiments of the device include a self-locking hollow member and measurement member. In one of these embodiments, the hollow member for advancement of the measurement member there through, and a measurement scale on the body, a light element placed within the distal portion of the measurement member, a handle attached to the proximal portion of the measurement member, a power supply housed within the handle, and a plurality of leads electrically coupling the power supply with the light element, wherein the leads extend from the power supply through the measurement member and to the light element. In one embodiment, the measurement member, the flange, and the hollow member are all manufactured from a plastic material. In another embodiment, the measurement member and the hollow member are manufactured from a metallic material. The device may also include a pressure controlling component that includes an outer sleeve surrounding the handle, wherein the outer sleeve has an outer shell with an interior space that includes a proximal region and a distal region, and a resilient element within the proximal region of the interior space. The handle is placed in the distal region of the interior space and distal to the resilient element.